Sensor and measurement method for measuring hydrogen content in metal melt

ABSTRACT

A sensor and a measurement method for measuring hydrogen content in metal melt. The sensor has a solid proton conductor element, a reference electrode, a quasi-electrode to be measured, a reference compound, a through pipe and an insulating ceramic adhesive. The measurement method has the steps of: (1) inserting the sensor and a corrosion-resistant electrode into the metal melt, and making sure that the solid proton conductor element is fully immersed into the metal melt, the quasi-electrode to be measured is in direct contact with the metal melt and the contact surface is the electrode to be measured; (2) connecting a potentiometer and the reference electrode cable or the metal gas guide pipe to the corrosion-resistant electrode, and measuring a potential difference between the reference electrode and the electrode to be measured; and (3) calculating the hydrogen content S of the metal melt.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a hydrogen measurement sensingtechnology, in particular to a sensor and measurement method formeasuring hydrogen content in metal melt.

2. The Prior Arts

In general, hydrogen is a harmful element in metal materials and cancause metal materials to produce defects such as hydrogen embrittlement,porosity and pinholes. Timely measurement of hydrogen content in metalsand proper dehydrogenation after information feedback can avoid varioushydrogen-induced defects in metal materials.

EP0544281 TYK discloses a device for measuring hydrogen content inaluminum melt by a solid proton conductor. The hydrogen content of themetal melt of 1000° C. or below such as aluminum melt can be measured.

Because the solid proton conductor hydrogen sensor can be used formeasuring hydrogen content in gas, the reference electrode and theelectrode to be measured of the solid proton conductor sensor are bothexternal porous electrodes. A reference substance with certain hydrogenpartial pressure is stuffed into the reference electrode, or gas withcertain hydrogen partial pressure is introduced, and the electrode to bemeasured is in contact with atmosphere to be measured, so that aconcentration cell is obtained.

The cell reaction is:

$\begin{matrix}{{H_{2}({high})} = {H_{2}({low})}} & (1) \\{{\Delta\; G} = {{{RT}\;\ln\;\frac{p_{H_{2}}^{low}}{p_{H_{2}}^{high}}} = {{- 2}\;{EF}}}} & (2)\end{matrix}$

A potentiometer is used for measuring the electromotive force of theconcentration cell. The hydrogen partial pressure of the referenceelectrode is known (the hydrogen partial pressure of the referenceelectrode can be higher or lower than that of the electrode to bemeasured), so that the hydrogen partial pressure of the atmosphere to bemeasured can be calculated, and the hydrogen content is calculated.

According to a probe and method for measuring hydrogen content disclosedby TYK, a solid proton conductor is used as the main body of the sensorprobe, the solid proton conductor and the metal melt are isolated by aceramic bushing, a ceramic cover or a porous material, and thereof, agas chamber is created between the proton conductor and the metal melt.The method for measuring hydrogen content in metal melt comprises thefollowing steps of establishing equilibrium hydrogen partial pressurebetween the metal melt and the gas chamber atmosphere in the sensorprobe, and measuring the hydrogen partial pressure according to aSievert's law:S=k√{square root over (p _(H) ₂ )}  (3)in the formula (3), S is the hydrogen content of metal melt, k is aconstant, and p_(H) ₂ is the equilibrium hydrogen partial pressure ofthe metal melt. At the moment, the hydrogen partial pressure ofatmosphere in a porous material is equilibrium hydrogen partial pressureof the metal melt, and the hydrogen content in the aluminum melt can beobtained through calculation.

US2005/0252789 proposes that a metal-hydrogen material with stablechemical stability such as αTi-βTi, αZr-βZr and αHf-βHf is taken as thereference substance of the sensor. The interface between the referencesubstance and the solid electrode can maintain chemical stability athigher temperature, influence of oxygen on the solid proton conductor isreduced, and stable hydrogen partial pressure is provided. However, thepatent does not refer to the measurement method of hydrogen content indetail.

US2009/0139876 discloses a device for measuring hydrogen content inmetal melt by using a solid proton conductor and proposes a method forrestoring the solid electrolyte of the proton conductor by using a waterabsorbing material such as AlN and BN.

According to the device and the method, the equilibrium hydrogen partialpressure established between the metal melt and the gas chamber in theprobe is measured by using the hydrogen concentration cell of the solidproton conductor. The method has the following disadvantages that: (1)time for establishing equilibrium between the metal melt and the gaschamber is long, which results in low sensor response speed; (2) thematerial for establishing the gas chamber in the sensor is usually theceramic cover or fiber materials, water is easy to adhere to thesurfaces of such materials, water reacts with the metal melt to producea large amount of hydrogen during measurement, and the accuracy ofmeasurement results is affected; and (3) during multiple measurementprocesses, the gas chamber is easy to block by metal and metal oxidesadhered to the surface of the probe, so that establishment ofequilibrium is slow, response speed is reduced and even measurementaccuracy is affected.

SUMMARY OF THE INVENTION

In accordance with the problems existing in the prior art, the presentinvention provides a sensor and measurement for measuring hydrogencontent in metal melt. A proton conductor in the sensor is in directcontact with the metal melt to form an electrode to be measured. It isnot necessary to establish hydrogen solubility equilibrium with themetal melt via gas for the electrode to be measured, but the protonconductor is adopted to directly establish electrochemical equilibriumbetween a reference substance and hydrogen in the metal melt.

The present invention adopts the following technical scheme ofproviding:

a sensor for measuring hydrogen content in metal melt, which comprises asolid proton conductor element, a reference electrode, a quasi-electrodeto be measured, a reference substance, a through pipe and an insulatingceramic adhesive, wherein the through pipe and the solid protonconductor element are connected through the insulating ceramic adhesiveto form an inner space, the surface located in the space, of the solidproton conductor element, is an inner surface, and the surface exposedoutside is an outer surface; the reference electrode is coated to theinner surface of the solid proton conductor element, and thequasi-electrode to be measured is the outer surface of the solid protonconductor element; the quasi-electrode to be measured is in contact withthe metal melt during hydrogen measurement, and the contact surfaceforms the electrode to be measured; and the reference substance isgas-phase reference substance, liquid-phase reference substance orsolid-phase reference substance, is placed in the inner space and is incontact with the reference electrode.

The sensor for measuring hydrogen content in metal melt can alsocomprise a gas guide pipe and a tee fitting. When the referencesubstance is gas-phase reference substance, the tee fitting is connectedwith the upper part of the through pipe, the gas guide pipe is insertedinto the inner space through the tee fitting and is connected to thereference electrode; when the bottom end of the gas guide pipe directlyfaces to the reference electrode and the solid proton conductor element,the bottom end of the gas guide pipe is a blind end, a side opening ofthe gas guide pipe acts as a gas outlet which has the effect ofpreventing pressure change caused by the gas-phase reference substancerushing at the reference electrode or the proton conductor element andimproving measurement accuracy.

The sensor for measuring hydrogen content in metal melt can alsocomprise a reference electrode cable. When the reference substance is agas-phase reference substance, the reference electrode cable is insertedinto the through pipe through the tee fitting, electrically connectedwith the reference electrode and externally connected to a measuringcircuit; when the reference substance is liquid-phase referencesubstance or solid-phase reference substance, a reference electrodecable penetrates through the insulating ceramic adhesive, iselectrically connected with the reference electrode and is externallyconnected to the measuring circuit.

The gas guide pipe is made of corundum, quartz, zirconium oxide,stainless steel, nickel-chromium alloy or iron-chromium-aluminum alloy.When the corundum, quartz or zirconium oxide gas guide pipe is used, thesensor comprises a reference electrode cable.

The tee fitting is made of stainless steel, copper, Teflon, nylon orpolyurethane.

The reference electrode cable is made of metal platinum, gold, silver,nickel-chromium alloy, iron-chromium-aluminum alloy or stainless steel.

When the reference substance is liquid-phase reference substance orsolid-phase reference substance, the sensor for measuring hydrogencontent in metal melt comprises an inert material of Al₂O₃, YSZ or Y₂O₃;and the inert material is stuffed between the reference substance andthe insulating ceramic adhesive.

The solid proton conductor element can adopt a tubular, spherical,flaky, discoid, cubic or cylindrical structure and is made of aperovskite or complex perovskite structure material.

The reference electrode is made of silver, platinum or gold.

The insulating ceramic adhesive is an alumina-based material.

The reference substance is gas-phase reference substance, liquid-phasereference substance or solid-phase reference substance, wherein thegas-phase reference substance comprises hydrogen and argon calibrationgas mixtures, hydrogen and nitrogen calibration gas mixtures, hydrogenand helium calibration gas mixtures, water vapor and oxygen calibrationgas mixtures or ammonia and nitrogen calibration gas mixtures, which isdoped or undoped with one or more inert gases, the liquid-phasereference substance comprises lithium and lithium hydride two-phasemixture, and the solid-phase reference substance comprises yttriumhydrogen solid solution, titanium hydrogen solid solution, zirconiumhydrogen solid solution or scandium hydrogen solid solution. When thereference substance is liquid-phase reference substance or solid-phasereference substance, the insulating ceramic adhesive is used to seal thereference substance to the side of the reference electrode.

The through pipe is made of corundum, quartz, graphite, stainless steel,Theron, SiC or LaCrO₃ and acts as a support and a gas path.

The method for measuring hydrogen content in a metal melt by using thesensor comprises the following process steps of (1) inserting the sensorand a corrosion-resistant electrode into the metal melt, and making surethat the solid proton conductor element is fully immersed into the metalmelt, the quasi-electrode to be measured is in direct contact with themetal melt and the contact surface is the electrode to be measured; (2)connecting a potentiometer and the reference electrode cable or the gasguide pipe which is metal to the corrosion-resistant electrode, andmeasuring potential difference between the reference electrode and theelectrode to be measured; and (3) calculating the hydrogen content S ofthe metal melt according to the measured potential difference, thetemperature of the metal melt and the saturated solubility of hydrogenin the metal melt, wherein the cell reaction equation and thecalculation formula are shown as (4) and (5):½H₂=[H]_(Metal)  (4)one atmospheric pressure and a 1% solution are taken as standard state;

$\begin{matrix}{{\Delta\; G} = {{{\Delta\; G^{\theta}} + {{RT}\;\ln\;\frac{a_{\lbrack H\rbrack}}{\sqrt{p_{H_{2}}^{ref}/p^{\theta}}}}} = {- {EF}}}} & (5)\end{matrix}$in the formula (5), ΔG is Gibbs free energy (J/mol); ΔG^(θ) is standardGibbs free energy (J/mol); R is gas constant (J/(K·mol)); T isthermodynamic temperature (K); a[H] is hydrogen activity; p_(H) ₂ ^(ref)is the hydrogen partial pressure of the reference substance (Pa); pθ isstandard pressure (Pa); E is electromotive force (V); and F is Faraday'sconstant (C/mol).

When equilibrium between hydrogen in the metal melt and hydrogen in theatmosphere is established, the following equation can be obtained:

$\begin{matrix}{{\Delta\; G} = {{{\Delta\; G^{\theta}} + {{RT}\;\ln\;\frac{a_{\lbrack H\rbrack}}{\sqrt{p_{H_{2}}^{Gas}/p^{\theta}}}}} = 0}} & (6)\end{matrix}$in the formula (6), p_(H) ₂ ^(Gas) is the equilibrium hydrogen partialpressure in the atmosphere;a _([H]) =f _([H]) ·w _([H])  (7)in the formula (7), f_([H]) is the activity coefficient of hydrogen inthe metal melt, and w_([H]) is the percentage by mass of hydrogen in themetal melt.

When hydrogen in the metal melt is saturated, the equilibrium hydrogenpartial pressure is one standard atmospheric pressure. At the moment,p_(H) ₂ ^(Gas)=p^(θ).ΔG=ΔG ^(θ) +RT ln a _([H])=0  (8)ΔG ^(θ) =−RT ln a _([H])  (9)

Because the saturated solubility of hydrogen in most of metals is verylow and obeys Henry's law, the activity coefficient f_([H]) is about 1,ΔG ^(θ) =−RT ln w _([H])  (10)

Because hydrogen in the metal melt is saturated, w_([H]) can be subjectto unit transformation by using the saturated solubility of hydrogen andput into the equation;ΔG ^(θ) =−RT ln KS ₀  (11)in the formula (11), S₀ is the saturated solubility of hydrogen (ml/100g), and K is a constant produced by unit transformation. Because thesaturated solubility S₀ of most of metals is known thermodynamic data orthermodynamic data which can be calculated, the standard Gibbs freeenergy ΔG^(θ) for hydrogen dissolving in the metal melt can becalculated.

Because the standard Gibbs free energy ΔG^(θ) for hydrogen dissolving inthe metal melt is only related to the kind and the temperature of themetal melt and does not change along with hydrogen content in the metalmelt, when hydrogen is saturated in the metal melt, the standard Gibbsfree energy ΔG^(θ) for hydrogen dissolving in the metal melt is the sameas that in unsaturation;

The formula (11) is put into the formula (5) to obtain:

$\begin{matrix}{{\Delta\; G} = {{{RT}\;\ln\;\frac{KS}{{KS}_{0}\sqrt{p_{H_{2}}^{ref}/p^{\theta}}}} = {- {EF}}}} & (12) \\{{\ln\; S} = {{\ln\; S_{0}\sqrt{p_{H_{2}}^{ref}/p^{\theta}}} - \frac{EF}{RT}}} & (13) \\{S = {\exp\;\left( {{\ln\; S_{0}\sqrt{p_{H_{2}}^{ref}/p^{\theta}}} - \frac{EF}{RT}} \right)}} & (14)\end{matrix}$

The hydrogen content S of the metal melt can be calculated. According todifferent natures of the selected solid proton conductor and the metalmelt to be measured, the formula (14) can be corrected according toexperiment results.

The sensor and the measurement method for measuring hydrogen content inmetal melt disclosed by the present invention have the beneficialeffects as followings:

1. For the sensor for measuring hydrogen content, the proton conductorcan be in direct contact with the metal melt, atmosphere of hydrogenequilibrium between the reference substance and the metal melt can beestablished quickly, the measurement speed is higher, the result is moreaccurate, the hydrogen measurement sensor is simpler after beingsimplified, and the hydrogen content of the metal melt of which thetemperature is lower than 1000° C. can be measured;

2. In the measurement method for measuring hydrogen content, thehydrogen content in the metal melt is directly calculated according tothe potential difference between the hydrogen in the reference substanceand hydrogen in the metal melt, the method is more visual and accurate,and the influence of instability of a gas chamber in a conventionalsensor on the measurement result is avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent to those skilled in the art byreading the following detailed description of a preferred embodimentthereof, with reference to the attached drawings, in which:

FIG. 1 is the diagram showing the process for measuring hydrogen contentin a metal melt by using the sensor of the present invention;

FIG. 2 is the structure diagram of the sensor for measuring hydrogencontent in the embodiment 1 of the present invention;

FIG. 3 is the structure diagram of the sensor for measuring hydrogencontent in the embodiment 2 of the present invention;

FIG. 4 is the structure diagram of the sensor for measuring hydrogencontent in the embodiment 3 of the present invention;

FIG. 5 is the structure diagram of the sensor for measuring hydrogencontent in the embodiment 4 of the present invention;

FIG. 6 is the structure diagram of the sensor for measuring hydrogencontent in the embodiment 5 of the present invention;

FIG. 7 is the structure diagram of the sensor for measuring hydrogencontent in the embodiment 6 of the present invention;

FIG. 8 is the structure diagram of the sensor for measuring hydrogencontent in the embodiment 7 of the present invention; and

FIG. 9 is the structure diagram of the sensor for measuring hydrogencontent in the embodiment 8 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

Embodiment 1

As shown in FIG. 1 and FIG. 2, the sensor for measuring hydrogen contentin aluminum melt comprises a CaZr_(0.9)In_(0.1)O_(3-α) solid protonconductor element 1, a reference electrode 2, a quasi-electrode 6 to bemeasured, a reference substance hydrogen and argon calibration gasmixtures, a stainless steel gas guide pipe 3, a corundum through pipe 5,an alumina-based insulating ceramic adhesive 4 and a Teflon tee fitting104, wherein the solid proton conductor element 1 adopts a tubularstructure and is made of perovskite, one end is sealed by thealumina-based insulating ceramic adhesive 4, the through pipe 5 and thesolid proton conductor element 1 are connected through the insulatingceramic adhesive 4 to form an inner space, the surface located in thespace, of the solid proton conductor element 1 is an inner surface, andthe surface exposed outside is an outer surface; the reference electrode2 is coated to the inner surface of the solid proton conductor element 1and the alumina-based insulating ceramic adhesive 4, and thequasi-electrode 6 to be measured is the outer surface of the solidproton conductor element 1; the upper part of the through pipe 5 isconnected through the Teflon tee fitting 104, and one side of the Teflontee fitting 104 is provided with a gas outlet 105; the referencesubstance hydrogen and argon calibration gas mixtures is introduced intothe inner space and is in contact with the reference electrode 2; andthe gas guide pipe 3 is inserted into the inner space through the Teflontee fitting 104 and is in contact with the reference electrode 2.

The reference electrode 2 is made of porous platinum.

For the reference substance hydrogen and argon calibration gas mixtures,the mole hydrogen content is 1.00%.

The method for measuring hydrogen content in a metal melt 101 which isaluminum melt by using the sensor comprises the following process stepsof (1) inserting the sensor and a graphite corrosion-resistant electrode102 into the metal melt 101 which is the aluminum melt of 750° C., andmaking sure that the solid proton conductor element 1 is fully immersedinto the metal melt 101, the quasi-electrode 6 to be measured is indirect contact with the metal melt 101 and the contact surface is theelectrode 100 to be measured; (2) connecting a potentiometer and the gasguide pipe 3 to the graphite corrosion-resistant electrode 102 through astainless steel wire 103, and measuring the potential difference betweenthe reference electrode 2 and the electrode 100 to be measured to be17.3 mV, wherein the gas guide pipe 3 is metal; and (3) calculating thehydrogen content S of the metal melt 101 according to the measuredpotential difference, the temperature of the metal melt 101 and thesaturated solubility of hydrogen in the metal melt 101, wherein the cellreaction equation and the calculation formula are shown as (4) and (5):

$\begin{matrix}{{\frac{1}{2}H_{2}} = \lbrack H\rbrack_{Metal}} & (4) \\{{\Delta\; G} = {{{\Delta\; G^{\theta}} + {{RT}\;\ln\;\frac{a_{\lbrack H\rbrack}}{\sqrt{p_{H_{2}}^{ref}/p^{\theta}}}}} = {- {EF}}}} & (5) \\{{\Delta\; G^{\theta}} = {{- {RT}}\;\ln\;{KS}_{0}}} & (11)\end{matrix}$in the formula (11), S₀ is the saturated solubility of hydrogen (ml/100g), and K is a constant produced by unit transformation. Because thesaturated solubility S₀ of most of metals is known thermodynamic data orthermodynamic data which can be calculated, the standard Gibbs freeenergy ΔG^(θ) for hydrogen dissolving in the metal melt 101 can becalculated.

Because the standard Gibbs free energy ΔG^(θ) for hydrogen dissolving inthe metal melt 101 is only related to the kind and the temperature ofthe metal melt 101 and does not change along with hydrogen content inthe metal melt 101, when hydrogen is saturated in the metal melt 101,the standard free energy ΔG^(θ) for hydrogen dissolving in the metalmelt 101 is the same as that in unsaturation;

The formula (11) is put into the formula (5) to obtain:

$\begin{matrix}{S = {\exp\;\left( {{\ln\; S_{0}\sqrt{p_{H_{2}}^{ref}/p^{\theta}}} - \frac{EF}{RT}} \right)}} & (14)\end{matrix}$

The electromotive force E is measured by the potentiometer, and thestabilized hydrogen content of the aluminum melt is calculated to beS=0.103 ml/100 gAl.

Embodiment 2

The sensor for measuring hydrogen content in metal melt 101 which isaluminum melt is the same as that in the embodiment 1, as shown in FIG.3. The difference lies in that: the sensor also comprises a referenceelectrode cable 7 which is made of metal platinum. The referenceelectrode cable 7 is inserted into the quartz through pipe 5 through thecopper tee fitting 104, is connected to the gold reference electrode 2and is externally connected to a measuring circuit; the gas guide pipe 3is made of corundum; the solid proton conductor element 1 is made ofCaZr_(0.9)Sc_(0.1)O_(3-α); the tee fitting 104 is made of copper; thethrough pipe 5 is made of quartz; and the reference electrode 2 is madeof porous gold.

The method for measuring hydrogen content in metal melt 101 by using thesensor comprises the following process steps of (1) inserting the sensorand a graphite corrosion-resistant electrode 102 into the aluminum meltof 750° C., and making sure that the solid proton conductor element 1 isfully immersed into the aluminum melt, the quasi-electrode 6 to bemeasured is in direct contact with the metal melt 101 and the contactsurface is the electrode 100 to be measured; (2) connecting apotentiometer and the reference electrode cable 7 to the graphitecorrosion-resistant electrode 102 through a platinum wire 103, andmeasuring the potential difference between the reference electrode 2 andthe electrode 100 to be measured; and (3) calculating the stabilizedhydrogen content S of the metal melt 101 according to the measuredpotential difference, the temperature of the metal melt 101 and thesaturated solubility of hydrogen in the metal melt 101 to be 0.113ml/100 gAl.

Embodiment 3

The sensor for measuring hydrogen content in aluminum melt is the sameas that in the embodiment 1, as shown in FIG. 4. The difference lies inthat: the solid proton conductor element 1 used in the sensor adopts aflaky structure; the through pipe 5 is made of stainless steel; one endbeing contact with the solid proton conductor element 1, of thenickel-chromium gas guide pipe 3 is a blind end, a side opening of thegas guide pipe 3 is used as a gas outlet, and a vertical distancebetween the gas outlet and the top end of the solid proton conductorelement 1 is 2-5 mm; the gas guide pipe 3 material is made ofnickel-chromium alloy; and the reference gas is hydrogen and heliumcalibration gas mixtures, and the mole hydrogen content is 1.00%.

The method for measuring hydrogen content in metal melt 101 by using thesensor comprises the following process steps of (1) inserting the sensorand a graphite corrosion-resistant electrode 102 into the aluminum meltof 750° C., and making sure that the solid proton conductor element 1 isfully immersed into the aluminum melt, the quasi-electrode 6 to bemeasured is in direct contact with the metal melt 101 and the contactsurface is the electrode 100 to be measured; (2) connecting apotentiometer and the nickel-chromium gas guide pipe 3 to the graphitecorrosion-resistant electrode 102 through a nickel-chromium wire 103,and measuring the potential difference between the reference electrode 2and the electrode 100 to be measured; and (3) calculating the stabilizedhydrogen content S of the aluminum melt according to the measuredpotential difference, the temperature of the metal melt 101 and thesaturated solubility of hydrogen in the metal melt 101 to be 0.109ml/100 gAl.

Embodiment 4

The sensor for measuring hydrogen content in aluminum melt is the sameas that in the embodiment 3, as shown in FIG. 5. The difference lies inthat: the sensor also comprises a reference electrode cable 7 which ismade of metal silver. The reference electrode cable 7 is inserted intothe through pipe 5 through the stainless steel tee fitting 104, isconnected with the silver reference electrode 2 and is externallyconnected to a measuring circuit; the through pipe 5 is made of quartz;the gas guide pipe 3 is made of corundum; the reference electrode 2 ismade of porous silver; and the reference gas is hydrogen and nitrogencalibration gas mixtures, and the mole hydrogen content is 1.00%.

The method for measuring hydrogen content in metal melt 101 by using thesensor comprises the following process steps of (1) inserting the sensorand a graphite corrosion-resistant electrode 102 into the aluminum meltof 750° C., and making sure that the solid proton conductor element 1 isfully immersed into the metal melt 101, the quasi-electrode 6 to bemeasured is in direct contact with the metal melt 101 and the contactsurface is the electrode 100 to be measured; (2) connecting apotentiometer and the reference electrode cable 7 to the graphitecorrosion-resistant electrode 102 through a silver wire 103, andmeasuring the potential difference between the reference electrode 2 andthe electrode 100 to be measured; and (3) calculating the stabilizedhydrogen content S of the aluminum melt according to the measuredpotential difference, the temperature of the metal melt 101 and thesaturated solubility of hydrogen in the metal melt 101 to be 0.130ml/100 gAl.

Embodiment 5

The sensor for measuring hydrogen content in aluminum melt is the sameas that in embodiment 3, as shown in FIG. 6. The difference lies inthat: the solid proton conductor element 1 used in the sensor adopts aspherical structure.

The method for measuring hydrogen content in metal melt 101 by using thesensor comprises the following process steps of (1) inserting the sensorand a graphite corrosion-resistant electrode 102 into the aluminum meltof 750° C., and making sure that the solid proton conductor element 1 isfully immersed into the aluminum melt, the quasi-electrode 6 to bemeasured is in direct contact with the metal melt 101 and the contactsurface is the electrode 100 to be measured; (2) connecting apotentiometer and the gas guide pipe 3 to the graphitecorrosion-resistant electrode 102 through a stainless steel wire 103,and measuring the potential difference between the reference electrode 2and the electrode 100 to be measured; and (3) calculating the stabilizedhydrogen content S of the aluminum melt according to the measuredpotential difference, the temperature of the metal melt 101 and thesaturated solubility of hydrogen in the metal melt 101 to be 0.123ml/100 gAl.

Embodiment 6

The sensor for measuring hydrogen content in aluminum melt is the sameas that in embodiment 5, as shown in FIG. 7. The difference lies inthat: the sensor also comprises a reference electrode cable 7 which ismade of stainless steel. The reference electrode cable 7 is insertedinto the through pipe 5 through the Teflon tee fitting 104, is connectedto the reference electrode 2 and is externally connected to a measuringcircuit; and the gas guide pipe 3 is made of corundum.

The method for measuring hydrogen content in metal melt 101 by using thesensor comprises the following process steps of (1) inserting the sensorand a graphite corrosion-resistant electrode 102 into the aluminum meltof 750° C., and making sure that the solid proton conductor element 1 isfully immersed into the aluminum melt, the quasi-electrode 6 to bemeasured is in direct contact with the metal melt 101 and the contactsurface is the electrode 100 to be measured; (2) connecting apotentiometer and the reference electrode cable 7 to thecorrosion-resistant electrode 102 through a stainless steel wire 103,and measuring the potential difference between the reference electrode 2and the electrode 100 to be measured; and (3) calculating the stabilizedhydrogen content S of the aluminum melt according to the measuredpotential difference, the temperature of the metal melt 101 and thesaturated solubility of hydrogen in the metal melt 101 to be 0.099ml/100 gAl.

Embodiment 7

As shown in FIG. 8, the sensor for measuring hydrogen content inaluminum melt comprises a solid proton conductor element 1, a referenceelectrode 2, an quasi-electrode 6 to be measured, a platinum-wire cable7, a solid-phase reference substance 8, a corundum through pipe 5, analumina-based ceramic adhesive 4 and an Al₂O₃ inert material 9, whereinthe solid proton conductor element 1 adopts a tubular structure and ismade of CaZr_(0.9)In_(0.1)O_(3-α), one end is sealed by using thealumina-based ceramic adhesive 4, the through pipe 5 and the solidproton conductor element 1 are connected through the insulating ceramicadhesive 4 to form an inner space, the surface located in the innerspace, of the solid proton conductor element 1 is an inner surface, andthe surface exposed outside is an outer surface; the reference electrode2 is coated to the inner surface of the solid proton conductor element1, and the quasi-electrode 6 to be measured is the outer surface of thesolid proton conductor element 1; the bottom of the solid protonconductor element 1 is stuffed with the Al₂O₃ inert material 9, theupper part is stuffed with the yttrium hydrogen solid solution systemsolid-phase reference substance 8, the reference substance 8 is incontact with the reference electrode 2 and the platinum-wire cable 7,the Al₂O₃ inert material 9 is stuffed to a space above the referencesubstance 8, and then the reference substance 8 is sealed by using thealumina-based ceramic adhesive 4 and is connected with the corundumthrough pipe 5; and the platinum-wire cable 7 penetrates through theinsulating ceramic adhesive 4, is connected with the reference electrode2 and is externally connected to a measuring circuit.

The reference electrode 2 is made of platinum.

The reference substance 8 is a yttrium hydrogen solid solution systemsolid, and the mole hydrogen content in equilibrium atmosphere of theyttrium hydrogen solid solution system solid at 750° C. is 0.11%.

The method for measuring hydrogen content in metal melt 101 by using thesensor comprises the following process steps of (1) inserting the sensorand a graphite corrosion-resistant electrode 102 into the aluminum meltof 750° C., and making sure that the solid proton conductor element 1 isfully immersed into the metal melt 101, the quasi-electrode 6 to bemeasured is in direct contact with the metal melt 101 and the contactsurface is the electrode 100 to be measured; (2) connecting apotentiometer and a platinum-wire cable 7 to the graphitecorrosion-resistant electrode 102 through a platinum wire 103, andmeasuring the potential difference between the reference electrode 2 andthe electrode 100 to be measured; and (3) calculating the stabilizedhydrogen content S of the aluminum melt according to the measuredpotential difference, the temperature of the metal melt 101 and thesaturated solubility of hydrogen in the metal melt 101 to be 0.107ml/100 gAl.

Embodiment 8

The sensor for measuring hydrogen content in aluminum melt is the sameas that in the embodiment 7, as shown in FIG. 9. The difference lies inthat: the solid proton conductor element 1 used in the sensor adopts aflaky structure and is made of CaZr_(0.9)Sc_(0.1)O_(3-α); the inertmaterial 9 is Y₂O₃; the reference substance is a scandium hydrogen solidsolution system solid, and the mole hydrogen content in equilibriumatmosphere of the scandium hydrogen solid solution system solid at 750°C. is 0.25%.

The method for measuring hydrogen content in metal melt 101 by using thesensor comprises the following process steps of (1) inserting the sensorand a graphite corrosion-resistant electrode 102 into the aluminum meltof 750° C., and making sure that the solid proton conductor element 1 isfully immersed into the aluminum melt, the quasi-electrode 6 to bemeasured is in direct contact with the metal melt 101 and the contactsurface is the electrode 100 to be measured; (2) connecting apotentiometer and a cable 7 to the graphite corrosion-resistantelectrode 102 through a platinum wire 103, and measuring the potentialdifference between the reference electrode 2 and the electrode 100 to bemeasured; and (3) calculating the stabilized hydrogen content S of thealuminum melt according to the measured potential difference, thetemperature of the metal melt 101 and the saturated solubility ofhydrogen in the metal melt 101 to be 0.143 ml/100 gAl.

What is claimed is:
 1. A sensor for measuring hydrogen content in metalmelt, comprising: a solid proton conductor element, a referenceelectrode, a quasi-electrode to be measured, a reference substance, athrough pipe and an insulating ceramic adhesive; wherein the throughpipe and the solid proton conductor element are connected through theinsulating ceramic adhesive to form an inner space, the surface locatedin the space, of the solid proton conductor element, is an innersurface, and the surface exposed outside, of the solid proton conductorelement, is an outer surface; the reference electrode is coated to theinner surface of the solid proton conductor element, and thequasi-electrode to be measured is the outer surface of the solid protonconductor element; the quasi-electrode to be measured is in contact withthe metal melt during hydrogen measurement, and the contact surfaceforms the electrode to be measured; and the reference substance isgas-phase reference substance, liquid-phase reference substance orsolid-phase reference substance, is placed in the inner space and is incontact with the reference electrode; and wherein the sensor furthercomprises a gas guide pipe and a tee fitting, and when the referencesubstance is gas-phase reference substance, the tee fitting is connectedwith an upper part of the through pipe, the gas guide pipe is insertedinto the inner space through the tee fitting and is connected to thereference electrode, and when a bottom end of the gas guide pipedirectly faces to the reference electrode and the solid proton conductorelement, the bottom end of the gas guide pipe is a blind end, a sideopening of the gas guide pipe acts as a gas outlet.
 2. The sensor formeasuring hydrogen content in metal melt according to claim 1, whereinthe sensor further comprises a reference electrode cable, and when thereference substance is gas-phase reference substance, the referenceelectrode cable is inserted into the through pipe through the teefitting, is connected with the reference electrode and is externallyconnected to a measuring circuit, and the reference electrode cable ismetal platinum, gold, silver, nickel-chromium alloy,iron-chromium-aluminum alloy or stainless steel.
 3. The sensor formeasuring hydrogen content in metal melt according to claim 1 whereinthe solid proton conductor element has a tubular, spherical, flaky,discoid, cubic or cylindrical structure and is made of a perovskite orcomplex perovskite structure material.
 4. The sensor for measuringhydrogen content in metal melt according to claim 1, wherein a materialof the reference electrode is silver, platinum or gold.
 5. The sensorfor measuring hydrogen content in metal melt according to claim 1,wherein a material of the insulating ceramic adhesive is analumina-based material.
 6. The sensor for measuring hydrogen content inmetal melt according to claim 1, wherein when the reference substance isgas-phase reference substance, liquid-phase reference substance orsolid-phase reference substance, the gas-phase reference substancecomprises hydrogen and argon calibration gas mixtures, hydrogen andnitrogen calibration gas mixtures, hydrogen and helium calibration gasmixtures, water vapor and oxygen calibration gas mixtures or ammonia andnitrogen calibration gas mixtures, which is doped or undoped with one ormore inert gases, the liquid-phase reference substance comprises lithiumand lithium hydride two-phase mixture, and the solid-phase referencesubstance comprises yttrium hydrogen solid solution, titanium hydrogensolid solution, zirconium hydrogen solid solution or scandium hydrogensolid solution.
 7. A method for measuring hydrogen content in metal meltby using the sensor for measuring hydrogen content in metal meltaccording to claim 1, the method comprising the following steps of: (1)inserting the sensor and a corrosion-resistant electrode into the metalmelt, and making sure that the solid proton conductor element is fullyimmersed into the metal melt, the quasi-electrode to be measured is indirect contact with the metal melt and the contact surface is theelectrode to be measured; (2) connecting a potentiometer and the gasguide pipe to the corrosion-resistant electrode, and measuring apotential difference between the reference electrode and the electrodeto be measured, wherein the gas guide pipe is metal, when the referencesubstance is gas-phase reference substance, the tee fitting is connectedwith an upper part of the through pipe, the gas guide pipe is insertedinto the inner space through the tee fitting and is connected to thereference electrode, and when a bottom end of the gas guide pipedirectly faces to the reference electrode and the solid proton conductorelement, the bottom end of the gas guide pipe is a blind end, a sideopening of the gas guide pipe acts as a gas outlet; and (3) calculatingthe hydrogen content S of the metal melt according to the measuredpotential difference, a temperature of the metal melt and a saturatedsolubility of hydrogen in the metal melt.
 8. A sensor for measuringhydrogen content in metal melt, comprising: a solid proton conductorelement, a reference electrode, a quasi-electrode to be measured, areference substance, a through pipe and an insulating ceramic adhesive;wherein the through pipe and the solid proton conductor element areconnected through the insulating ceramic adhesive to faun an innerspace, the surface located in the space, of the solid proton conductorelement, is an inner surface, and the surface exposed outside, of thesolid proton conductor element, is an outer surface; the referenceelectrode is coated to the inner surface of the solid proton conductorelement, and the quasi-electrode to be measured is the outer surface ofthe solid proton conductor element; the quasi-electrode to be measuredis in contact with the metal melt during hydrogen measurement, and thecontact surface forms the electrode to be measured; and the referencesubstance is gas-phase reference substance, liquid-phase referencesubstance or solid-phase reference substance, is placed in the innerspace and is in contact with the reference electrode; and wherein thesensor comprises a reference electrode cable, wherein when the referencesubstance is liquid-phase reference substance or solid-phase referencesubstance, the reference electrode cable penetrates through theinsulating ceramic adhesive, is connected with the reference electrodeand is externally connected to a measuring circuit, and the referenceelectrode cable is metal platinum, gold, silver, nickel-chromium alloy,iron-chromium-aluminum alloy or stainless steel.
 9. The sensor formeasuring hydrogen content in metal melt according to claim 8, whereinwhen the reference substance is liquid-phase reference substance orsolid-phase reference substance, the sensor further comprises an inertmaterial of Al₂O₃, YSZ or Y₂O₃; and the inert material is stuffedbetween the reference substance and the insulating ceramic adhesive. 10.The sensor for measuring hydrogen content in metal melt according toclaim 8, wherein the solid proton conductor element has a tubular,spherical, flaky, discoid, cubic or cylindrical structure and is made ofa perovskite or complex perovskite structure material.
 11. The sensorfor measuring hydrogen content in metal melt according to claim 8,wherein a material of the reference electrode is silver, platinum orgold.
 12. The sensor for measuring hydrogen content in metal meltaccording to claim 8, wherein a material of the insulating ceramicadhesive is an alumina-based material.
 13. The sensor for measuringhydrogen content in metal melt according to claim 8, wherein when thereference substance is gas-phase reference substance, liquid-phasereference substance or solid-phase reference substance, the gas-phasereference substance comprises hydrogen and argon calibration gasmixtures, hydrogen and nitrogen calibration gas mixtures, hydrogen andhelium calibration gas mixtures, water vapor and oxygen calibration gasmixtures or ammonia and nitrogen calibration gas mixtures, which isdoped or undoped with one or more inert gases, the liquid-phasereference substance comprises lithium and lithium hydride two-phasemixture, and the solid-phase reference substance comprises yttriumhydrogen solid solution, titanium hydrogen solid solution, zirconiumhydrogen solid solution or scandium hydrogen solid solution.
 14. Amethod for measuring hydrogen content in metal melt by using the sensorfor measuring hydrogen content in metal melt according to claim 8, themethod comprising the following steps of: (1) inserting the sensor and acorrosion-resistant electrode into the metal melt, and making sure thatthe solid proton conductor element is fully immersed into the metalmelt, the quasi-electrode to be measured is in direct contact with themetal melt and the contact surface is the electrode to be measured; (2)connecting a potentiometer and the reference electrode cable to thecorrosion-resistant electrode, and measuring a potential differencebetween the reference electrode and the electrode to be measured,wherein when the reference substance is liquid-phase reference substanceor solid-phase reference substance, the reference electrode cablepenetrates through the insulating ceramic adhesive, is connected withthe reference electrode and is externally connected to a measuringcircuit, and the reference electrode cable is metal platinum, gold,silver, nickel-chromium alloy, iron-chromium-aluminum alloy or stainlesssteel; and (3) calculating the hydrogen content S of the metal meltaccording to the measured potential difference, a temperature of themetal melt and a saturated solubility of hydrogen in the metal melt.